Given x squared + 5x minus 1 = 0, find the value of x minus 1 / X and 1 / X squared

Given x squared + 5x minus 1 = 0, find the value of x minus 1 / X and 1 / X squared

x^2+5x-1=0
Divide two sides by X to get: x + 5-1 / x = 0
That is, X-1 / x = - 5
Square of two sides: x ^ 2-2x * 1 / x + 1 / x ^ 2 = 25
That is, x ^ 2 + 1 / x ^ 2 = 25 + 2 = 27

How many hours is two-thirds of an hour

Take x = 2 and x = - 2 respectively, the other two results are equal, and K = 7 / 2

The perimeter of a rectangular playground is 300 meters. Now the length and width of the playground will be increased by 10 meters respectively. The area of the increased part is 300 meters______ Square meters

Suppose: the length of the original playground is a meter and the width is B meter. The sum of the length and width of the original playground is 300 △ 2 = 150 (meters), that is, a + B = 150 (meters). The length of the increased playground is a + 10 (meters), the width of the increased playground is B + 10 (meters), and the increased area is 10 × (B + 10) + 10a, = 10 × (a + B + 10), = 10 × (150 + 10), = 10 × 160, = 1600 (square meters) ）A: the additional area is 1600 square meters

In the triangle ABC, the angle a is 60 degrees and the length of the side BC is 3
A. 4 with 3sin (B + 60 degrees) + 3
B. 4 with 3sin (B + 30 degrees) + 3
C. 6 with 3sin (B + 60 degrees) + 3
D. 6 with 3sin (B + 30 degrees) + 3
This problem chooses d to use the sine theorem

If it is a multiple choice question, you can use the special value method to make it easier
It's difficult to work out this problem, which is a waste of time
Triangle ABC can be taken as equilateral triangle or right triangle

Try to compare the size of X & # 178; + 2x + 5 and - 2x + 1

∵﹙x²＋2x＋5﹚－﹙﹣2x＋1﹚
＝x²＋2x＋5＋2x－1
＝x²＋4x＋4
＝﹙x＋2﹚²≥0
∴ x²＋2x＋5≥﹣2x＋1.

One day at 2:00 p.m., the shadow length of a flagpole and a big tree is 6 meters and 4 meters respectively
1: It is known that the flagpole is 15 cm high. How many meters is this big tree high?
2: At 4:00 p.m., the shadow of the tree is 6 meters long. Can you find out how long the shadow of the flagpole is?

1. Suppose the height of the tree is X
So 15:6 = x: 4
X = 10m
The height of the big tree is 10 meters
2. Suppose the shadow length of the flagpole is y
10:6=15:y
Y = 9 m
The flagpole is 9 meters long

What's in the brackets? Why? It's a second grade rule,
7 9 8
8 15 ( )
5 4 4 3 2 7

7*(8-2)=42

If (X-5 / a) + (x + 2 / b) = x ^ 2-3x-10 / 5x-4, find the value of a and B

A/(x-5)+B/(x+2)=(5x-4)/(x^2-3x-10)
Ax+2A+Bx-5B=5x-4
A+B=5
2A-5B=-4
2A+2B=10-7B+-14
B=2,A=3

On the plan of an experimental field, a line of 3cm represents the actual distance of 90m. The scale of this map is
The distance on the map is 10 times of the actual distance. The scale of this map is (). If you measure the distance of 20 cm on the map, the actual distance is () cm

If the distance on the map is 10 times the actual distance, the scale of the map is 10:1
If you measure a distance of 20 cm on the graph, the actual distance is 2 cm

A barrel of oil weighs 8 kg. After 2 / 7 of it is used, the whole barrel weighs 6 kg
There are 55 students in a class. In a math test, the average score of boys is 89, that of girls is 90.1, and that of the whole class is 89.6. The simplest integer ratio of girls to boys in this class is ()

A barrel of oil weighs 8 kg. After 2 / 7 of it is used, the whole barrel weighs 6 kg
There are 55 students in a class. In a math test, the average score of boys is 89, that of girls is 90.1, and that of the whole class is 89.6. The simplest integer ratio of girls to boys in this class is (6:5)